The present invention relates to an air filter arrangement for an internal combustion engine including a housing, in which an air filter element is arranged and which is located between an unfiltered air intake in an unfiltered air capsule and a filtered air outlet in a filtered air capsule, and a membrane which covers an orifice contained within the housing.
An air filter for an internal combustion engine in a vehicle, which is designed to transmit sound into the passenger compartment, is known from German publication DE 199 40 610 A1. To that end, a housing orifice is provided in the air filter housing through the use of an oscillating and airtight membrane. As the membrane is made of a material more permeable to sound than the housing wall, the shape and position of the membrane can be used to achieve specific sound generation and distribution.
One object of this invention is to design an air filter housing in such a way as to render it capable of having an acoustic effect on the exterior and interior sounds of vehicles and to enable integration of a sound device, by way of a simple mounting process, into the air filter housing.
This object is achieved according to the invention by providing an air-permeable and fine-mesh fabric or a thin-walled sound element covering a housing orifice with at least one perforation contained in the unfiltered air capsule or the filtered air capsule for airborne sound emission. Additional advantageous features are included in the dependent claims.
The invention advantageously enables sound components in the intake tract to be emitted via orifices in the air filter housing, which are covered by fabric or a thin-walled sound element, in such a way as to cause the vehicle to emit a pleasant exterior and interior sound. This is basically accomplished by equipping, for the purpose of airborne sound emission, the unfiltered air or filtered air capsule of the air filter housing with a housing orifice containing at least one perforation, which is covered by an air-permeable and fine-meshed structured fabric or thin-walled sound element. The fabric can be water-repellent or watertight. The perforations are preferably provided in an insert part, which is introduced into the housing orifice. The fabric or sound element can also be clamped between two perforated insert parts in the housing orifice, and the housing orifice is closed in an air-permeable manner. Furthermore, an embodiment in which the perforations are molded into the housing wall and are then covered by the fabric or the sound element is also conceivable.
A housing orifice with perforations, covered by fabric or by the sound element, advantageously enables, for example, the emission of sound components in the intake tract via the housing orifice. In particular, perforations that are adjusted to the desired interior and exterior sound can be arranged in the housing wall; that is, it is possible to arrange for a certain number of orifices or a certain geometrical shape, or even a certain diameter of the orifices.
In order to prevent the perforated insert parts with the fabric or sound element arranged between them from transmitting impact sounds made by the fabric or the sound element at the time of a sudden change in pressure, impact dampers can be provided on the insert parts. The fabric can also be glued onto the perforation.
The fabric used is a so-called industrial fabric, which can be made impermeable to water, rain and dirt, etc. This fabric is so finely meshed as to avoid the inconvenient intake of warm air from the engine compartment during a “warm start”. The fabric allows only a small amount of flow during starting, idle and partial load of the internal combustion engine. During air circulation at higher rates, for example when the internal combustion engine is fully loaded, the fabric, as a function of its structure, can allow a greater portion of the intake air to pass through. This leads to a reduction in the pressure ratio of the intake system and can be used to increase the engine power. Due to the different rates of air intake in the various operating conditions of the motor, an advantageous separation between warm and cold intake air components is possible.
According to another embodiment of the invention, a wall containing a perforation is molded onto the housing wall forming the housing orifice, and the membrane formed of the fabric or the thin-walled sound element is arranged between this wall and an attached insert part containing perforations.
Furthermore, the membrane formed of the fabric or the sound element can be connected to a frame, which is arranged above or beneath a housing orifice and is connected to the housing.
Embodiments of the invention are shown in the drawings and are explained in greater detail below.